Biology

To be clear, human chimeras already exist naturally, from the fusion of twin embryos in utero. Most of them go entire lives without even realizing it. Only occasionally it pops up in the news when someone receives a negative paternity test and after lots of stress and hairpulling and doctor's visits it turns out that their blood comes from a different cell line than their balls.

Human-ape chimeras are the stuff of bioethicists' nightmares and thankfully illegal everywhere civilized.